Alarm circuit

ABSTRACT

Two monostable multivibrators are interconnected to provide a single alarm output whenever a signal is applied to the circuit over a first input lead, and to provide a repetitive alarm output whenever a signal is applied to the circuit over a second input lead. The alarm is driven by the output from the first multivibrator, which output occurs once with each individual signal applied over the first input lead. Whenever a signal is applied over the second input lead the two multivibrators operate alternately for the duration of the signal, the output from the first multivibrator both driving the alarm and providing an input to the second multivibrator, and the output from the second multivibrator providing an input to the first multivibrator.

United States Patent Heneghan {4514 Sept. 12, 1972 [54] ALARM CIRCUIT 72 Inventor: Patrick J. Heneghan, Chicago, 111. j' g 'ff-g a a fiffif 0rne-. anisan ler [73] Assignee: Teletype Corporation, Skokie, Ill. y

221 Filed: Aug. 19, 1970 [571 ABSTRACT 2 APPL 5,0 Two rnonostable multivibrators are interconnected to provide a single alarm output whenever a signal is applied to the circuit over a first input lead, and to pro- [52] US. Cl. ..340/248 P, 328/157 vide a repetitive alarm output whenever a signal is [51] llll. Cl. ..G08b 21/00 plied to the circuit over a second input lead The [58] Flew Search 3 alarm is driven by the output from the first multivibra- 331/57 328/143 69 tor, which output occurs once with each individual 307/231 signal applied over the first input lead. Whenever a signal is applied over the second input lead the two [56] References Cited multivibrators operate alternately for the duration of UNITED STATES PATENTS the signal, the output from the firstmultivibrator both driving the alarm and providing an input to the second 2,984,789 5/1961 0 Br1en ..340/248 P multivibrator, and the output f he second E is; 8 tivibrator providing an input to the first multivibrator. am 3,500,369 3/1970 Kellam ..340/248 P 11 Claims, 3 Drawing Figures 39 so '2 SIGNAL l 38 3 34 SOURCE 0R '7 MONOSTABLE 22 MP 7 E MULTIVIBRATOR 2; W l8 -1'\ ALARM 1 40 2o MONOSTABLE 26 Saga; 1 1 MULTIVIBRATOR ALARM CIRCUIT BACKGROUND OF THE INVENTION The present invention relates to an alarm circuit, and in particular to an alarm circuit for providing either a single or a repetitive alarm output.

In maintaining attended and unattended sending and receiving teletypewriter terminals there is a need for alarm devices to occasionally call an operators attention to a terminal. It is desirable, for example, to signal an operator that the paper record medium in an attended sender terminal is almost at the end of a line of type so that the operator may advance the paper one or more lines, or to signal the operator, by a signal generated at an associated transmitting teletypewriter apparatus, that the incoming message is important, so that the operator will direct his immediate attention to it. It is further desirable that the alarm device he capable of generating two types of signals, such as a single signal output or a repetitive signal output, the first to direct the operators attention to a subcritical condition existing at the machine, that is, a condition which must be corrected but that doesnt require the operators immediate attention, and the second to call the operators attention to a critical condition existing at the machine which requires the operators immediate attention.

An object of the invention is to provide an alarm circuit for selectively providing either a single or a repetitive alarm output.

SUMMARY OF THE INVENTION The foregoing and other objects of theinvention are accomplished by providing first and second monostable multivibrators, the first multivibrator being constantly enabled to provide an output in response to an input signal at a trigger input, and the second multivibrator having both a trigger and an enabling input. The output of the second multivibrator is capacitor coupled to a first input of a gate, the output of which gate is connected to the trigger input of the first multivibrator; and the output of the first multivibrator is capacitor coupled to the trigger input of the second multivibrator. A first input line is connected to provide a second input to the gate and a second input line is connected to provide an enabling input to the second multivibrator, the second input line also being capacitor coupled to a third input of the gate. An indicator device, such as an audible alarm, is connected to receive output pulses from the first multivibrator, so that an input signal on the first input line operates to trigger the first multivibrator to provide a single output from the alarm. An input signal on the second input line operates to both trigger the first multivibrator and to enable the second multivibrator, the subsequent termination of the output from the first multivibrator operating to trigger the second multivibrator and the termination of the output from the second multivibrator operating to again trigger the first multivibrator, the first and the second multivibrators being alternately triggered, so that a repetitive output is provided by the alarm in response to the triggering of the first multivibrator.

Other objects, advantages and features of the invention will be apparent from the following detailed description of a specific embodiment thereof, when taken in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE INVENTION FIG. 1 is a block diagram of a preferred embodiment of the invention;

FIG. 2 is a timing diagram illustrating waveforms during the operation of the system shown in FIG. 1 in the mode producing a single alarm; and

FIG. 3 is a timing diagram illustrating waveforms during the operation of the system shown in FIG. 1 in the mode producing a repetitive alarm.

DETAILED DESCRIPTION Referring to FIG. 1 of the drawings, there is shown a selectively regenerative alarm circuit particularly adaptable for operation as a signaling device for a teletypewriter sending or receiving terminal. In the description of the operation of the circuit shown in the drawing, reference will be made to negative and to ground potentials. These terms for defining the potentials used in the circuit are relative terms used to illustrate the operation of the circuit and are not to be considered limiting, since any other two potentials could be used, the potential being substituted for the ground potential referred to in the specification being merely more positive than the potential being substituted for the negative potential.

The specific embodiment of the selectively regenerative alarm circuit 10 includes two conventional monostable multivibrators l2 and 14 having, for the purpose of this embodiment of the invention, a quasistable period of 500 milliseconds, the multivibrator 12 having a trigger input 16 and a continuous enable input 17 and the multivibrator 14 having both a trigger input 18 and an enable input 20. The multivibrator 12 is continuously enabled to provide an output in response to an appropriate input signal at the input 16, both multivibrators 12 and 14 being characterized in that a positive going transition applied to their trigger input in the presence of a positive potential enabling input signal switches the multivibrators to their quasistable state and provides a negative going transition at the output of the multivibrator for a time interval of 500 milliseconds. It is to be appreciated that any predetermined quasi-stable period other than 500 milliseconds could be obtained from the multivibrators, the difference merely being in the selection of the particular resistors and capacitors within the multivibra tors which control the time duration of the quasi-stable period of the multivibrator.

The output 22 of the multivibrator 12 is coupled to the trigger input 18 of the multivibrator 14 through a coupling capacitor 24, and the output 26 of the mul tivibrator 14 is coupled to a first input of an OR-gate 30 through a coupling capacitor 32, the output of which OR-gate 30 is connected to the trigger input 16 of the multivibrator 12. The output 22 of the multivibrator 12 also provides an input to an amplifier 34, the output of which drives an audible alarm device 36, such as a horn or a buzzer, upon the receipt of a negative potential input. An input signal line 38 having a terminal 39, and

' an input signal line 40 having a terminal 41, are proto a third input of the OR-gate 30 through a coupling capacitor 44. Two signal sources 43 and 45 selectively provide negative or ground potential signals to the terminals 39 41, respectively.

OPERATION Referring to FIG. 2, the continuously enabled multivibrator 12 is designed to provide a single output pulse 46 (-V in the example) lasting a predetermined time At, (500 milliseconds for the particular embodiment of the invention) after a positive (ground in the example) transition input signal 48 is applied by the signal source 43, to the input terminal 39, through the gate 30 and to the trigger input 16 of the multivibrator 12. Referring to FIG. 3, the multivibrator 12 is designed to produce a plurality of output pulses 46, each lasting the predetermined time At,, and the multivibrator 14 is designed to produce a plurality of output pulses 50 (V in the example), each lasting a predetermined time At (500 milliseconds for the particular embodiment of the invention), in response to a positive transition input signal 52 applied to the input terminal 41 by the signal source 45, the pulses 46 and 50 occurring in an alternate sequence with the beginning (negative transition) of each pulse occurring upon the termination (positive transition) of the opposite pulse.

To follow the operation of the circuit when the positive transition input signal 48 is applied to the input terminal 39 at a time t, in FIG. 2, the signal 48 is passed by the gate 30 to the trigger input 16 of the continuously enabled multivibrator l2, switching the multivibrator 12 to its quasi-stable state and providing a negative output pulse 46 therefrom, which pulse is applied as an input to the amplifier 34 which in turn drives the audible alarm 36 for as long as the output of the multivibrator 12 remains at a V potential. After a time interval of At, the multivibrator 12 returns to its stable state, allowing the potential at the output 22 to return from a V to a ground potential to deenergize the alarm device 36. Upon the return of the multivibrator 12 to its stable state, the positive transition provided at the output 22 is passed by the coupling capacitor 24 to the trigger input 18 of the multivibrator 14 providing an input thereto. However, unless a ground potential enabling signal is present at the enabling input 20 of the multivibrator 14 at the time that the positive transition signal is applied to the trigger input 18 through the capacitor 24, the multivibrator 14 will not be switched to its quasi-stable state and the alarm circuit will remain dormant until the input signal 48 first returns to a V potential and thereafter again rises to a ground potential.

, Therefore, it is seen that when a positive transition signal is applied to the input terminal 39 while a negative potential is applied to the input terminal 41, a single output is obtained from the multivibrator l2 and, therefore, from the alarm device 36, until the input signal at the terminal 39 first returns to its V potential and again rises to a ground potential. In this instance the multivibrator 14 remains unresponsive to the positive signal transition applied to the trigger input 18 through the coupling capacitor 24 from the output 22 of the multivibrator 12 as a result of the V potential applied to the enable input 20 from the input terminal 41.

To follow the operation of the alarm circuit 10 when a positive transition input signal 52 is applied to the input terminal 41 commencing at a time t, is FIG. 3, the positive transition is passed by the capacitor 44 to an input of the gate 30, which in turn applies the positive transition to the trigger input 16 of the multivibrator 12. The constantly enabled multivibrator 12 is switched to its quasi-stable state and provides a V potential at the output 22, which potential is applied to the amplifier 34 to energize the alarm device 36. Simultaneously, the positive signal 52 appearing at the input terminal 41 is applied to the enable input 20 of the multivibrator 14, thereby enabling the multivibrator 14 to switch to its quasi-stable state in response to a positive signal transition at its trigger input 18. After the time interval At,, at time t, in FIG. 3 of the drawings, the multivibrator 12 returns to its stable state, providing a positive transition signal (from V to ground) at its output 22 and deenergizing the alarm device 36. The positive transition at time t is passed by the capacitor 24 and applied to the trigger input 18 of the multivibrator 14. Since at this time a ground potential is being applied to the enable input 20 of the multivibrator 14, the multivibrator 14 responds to the positive transition at the trigger input 18 by switching to its quasi-stable state and providing a V potential at its output terminal 26. At time t;,, after the time interval At,, the multivibrator 14 returns to its stable state and provides a positive going signal transition at the output terminal 26 as the potential at the terminal rises from a V potential to a ground potential.

It is to be noted that during the At, time interval from t, to t the multivibrator 12 remained in its stable state, providing a ground potential at the output 22 and maintaining the alarm device 36 in a de-energized condition. At time t, the positive signal transition occurring at the output 26 of the multivibrator 14, as the multivibrator 14 returns to its stable state, is passed by the capacitor 32 and applied as an input to the gate 30 which in turn applies the positive signal transition to the trigger input 16 of the continuously enabled multivibrator 12, thereby driving the multivibrator 12 to its quasi-stable state once again, energizing the alarm device 36, and initiating a repeat of the cycle above described.

As may be seen in FIG. 3 of the drawings, the multivibrators 12 and 14, upon an application of the positive transition signal 52 to the terminal 41, will alternately switch from their stable to their quasi-stable states, the multivibrator 14 switching to its quasi-stable state for a time interval At, upon the return of the multivibrator 12 to its stable state, and the multivibrator l2 switching to its quasi-stable state for a time At, upon the return of the multivibrator 14 to its stable state, until the signal 52 is returned to a V potential. When the signal 52 is returned to a negative potential, the signal applied to the enable input 20 of the multivibrator 14 returns to a negative potential from a ground potential, thereby rendering the multivibrator 14 unable to be switched to its quasi-stable state upon the application of a positive transition to its trigger input 18, and terminating the repetitive alarm cycle upon the return of the signal at the output 22 of the multivibrator 12 to a ground potential after the signal 52 has been returned to a negative potential.

As described above, the alarm circuit 10 provides a single alarm output for a time interval At, upon the application of a positive transition signal 48 to the input terminal 39 by the signal source 43, and provides an intermittent and repetitive alarm output upon the application of, and for the duration of, a positive transition signal applied to the input terminal 41 by the signal source 45, the alarm in this instance being energized for intermittent time intervals At which time intervals At are separated from each other by time intervals At,. It is to be noted that while the time interval At provided by the multivibrator 22 and the time interval At provided by the multivibrator 14 are shown in a specific embodiment of the invention to be both equal to 500 milliseconds in duration and to each other, it is to be understood that the time intervals At and At; may be either greater than or less than 500 milliseconds and must not of necessity be equal, but may be varied to fit the particular application to which the alarm circuit is put.

While one specific embodiment of the invention has been described in detail, it will be obvious that various modifications may be made from the specific details described without departing from the spirit and scope of the invention. For example, negative logic employing ground to potential signals may be used instead of positive logic employing V to ground potential signals as described. In this instance, it would merely be necessary to substitute an AND-gate for the OR-gate 30, to substitute two multivibrators, which are responsive to a negative input signal transition to switch to their quasi-stable state and which provide a positive signal transition at their output upon switching to their quasi-stable state, for the two multivibrators 12 and 14, and to substitute an alarm device which is responsive to a +V potential input to energize and to a ground potential input to de-energize.

What is claimed is:

1. A selectively regenerative circuit, which comprises:

first and second means for producing a single output pulse after first and second predetermined times, respectively, in response to an input signal;

means for applying a first input signal to the first pulse producing means only, in order to actuate the first pulse producing means to produce an output pulse therefrom;

an indicator responsive to the output pulse from the first pulse producing means to provide an indication;

means for applying a second input signal to both the first and the second pulse producing means in order to actuate the first pulse producing means in order to produce an indication;

said second pulse producing means responsive to the coincidence of the output of the first pulse producing means and the second input signal for actuating the second pulse producing means to produce a single output pulse the second predetermined time after the output of the first pulse producing means; and

means coupling the output of the second pulse producing means for actuating the first pulse producing means to provide a second output pulse therefrom the first predetermined time after the output of the second pulse producing means, thereby providing repetitive indications.

2. A circuit as recited in claim 1 wherein the first and second output pulse producing means are first and second monostable multivibrators, the first multivibrator having a trigger input and the second multivibrator having both a trigger input and an enabling input.

3. A circuit as recited in claim 2, wherein:

the first input signal applying means comprises a first input signal line and a gate, the first input signal line providing an input to the gate and the gate providing an input to the trigger input of the first multivibrator; and

the second input signal applying means comprises a second input signal line connected to the enable input of the second multivibrator and a capacitor connected between the second input signal line and an input to the gate.

4. A circuit as recited in claim 3, wherein the means responsive to the output of the first pulse producing means and the second input signal for actuating the second pulse producing means comprises a capacitor connected between the output of the first pulse producing means and the trigger input of the second pulse producing means.

5. A circuit as recited in claim 4, wherein the means responsive to the output of the second pulse producing means for actuating the first pulse producing means comprises a capacitor connected between the output of the second pulse producing means and an input to the gate.

6. A circuit as recited in claim 5, wherein the indica tor is an audible alarm.

7. A selectively regenerative circuit, which comprises:

first and second monostable multivibrators, each capable of receiving an input signal and generating an output pulse of a predetermined length in response thereto, the first multivibrator having a trigger input and the second multivibrator having both a trigger and an enabling input;

means for coupling the output of the first multivibrator to the trigger input of the second multivibrator to provide an input thereto to trigger the second multivibrator upon the termination of the output pulse from the first multivibrator;

a gate, the output of the gate being connected to the trigger input of the first multivibrator to provide an input thereto;

means for coupling the output of the second multivibrator to the gate to provide a first input thereto to trigger the first multivibrator upon the termination of the output pulse from the second multivibrator;

an indicator device for receiving output pulses from the first multivibrator and for providing an output in response thereto;

first and second input lines, the first input line connected to provide a second input to the gate and the second input line providing an input to the enabling input of the second multivibrator;

means for coupling the second input line to the gate to provide a third input thereto; and

means for selectively applying an input signal to the first or the second input lines, whereby an input signal on the first input line operating to trigger the first multivibrator to provide a single output from the indicator device, and an input signal on the 9. A circuit as recited in claim 8, wherein each second input line operating to both trigger the first coupling means comprises a capacitor. multlvlbralof, and t enable the Second 10. A circuit as recited in claim 9, wherein the first tivibrator, so that the termination of the output from the first multivibrator operates to trigger the second multivibrator and so that the termination of the output from the second multivibrator operates to trigger the first multivibrator, the first and second multivibrators thereby being altemately triggered to provide a repetitive output from the 10 amplifier; and indicator device in response to the repetitive triggering of the first multivibrator. the output pullse o}: the multivibrator provides an 8. A circuit as recited in claim 7, wherein at least one Input Slgna to t e amp of the coupling means comprises a capacitor.

multivibrator is constantly enabled to provide an out- 5 put pulse in response to an input signal.

1 l. A circuit as recited in claim 10, wherein: the indicator device is an audible alarm device; an amplifier is connected to provide an input to the alarm device in response to an input signal to the 

1. A selectively regenerative circuit, which comprises: first and second means for producing a single output pulse after first and second predetermined times, respectively, in response to an input signal; means for applying a first input signal to the first pulse producing means only, in order to actuate the first pulse producing means to produce an output pulse therefrom; an indicator responsive to the output pulse from the first pulse producing means to provide an indication; means for applying a second input signal to both the first and the second pulse producing means in order to actuate the first pulse producing means in order to produce an indication; said second pulse producing means responsive to the coincidence of the output of the first pulse producing means and the second input signal for actuating the second pulse producing means to produce a single output pulse the second predetermined time after the output of the first pulse producing means; and means coupling the output of the second pulse producing means for actuating the first pulse producing means to provide a second output pulse therefrom the first predetermined time after the output of the second pulse producing means, thereby providing repetitive indications.
 2. A circuit as recited in claim 1 wherein the first and second output pulse producing means are first and second monostable multivibrators, the first multivibrator having a trigger input and the second multivibrator having both a trigger input and an enabling input.
 3. A circuit as recited in claim 2, wherein: the first input signal applying means comprises a first input signal line and a gate, the first input signal line providing an input to the gate and the gate providing an input to the trigger input of the first multivibrator; and the second input signal applying means comprises a second input signal line connected to the enable input of the second multivibrator and a capacitor connected between the second input signal line and an input to the gate.
 4. A circuit as recited in claim 3, wherein the means responsive to the output of the first pulse producing means and the second input signal for actuating the second pulse producing means comprises a capacitor connected between the output of the first pulse producing means and the trigger input of the second pulse producing means.
 5. A circuit as recited in claim 4, wherein the means responsive to the output of the second pulse producing means for actuating the first pulse producing means comprises a capacitor connected between the output of the second pulse producing means and an input to the gate.
 6. A circuit as recited in claim 5, wherein the indicator is an audible alarm.
 7. A selectively regenerative circuit, which comprises: first and second monostable multivibrators, each capable of receiving an input signal and generating an output pulse of a predeteRmined length in response thereto, the first multivibrator having a trigger input and the second multivibrator having both a trigger and an enabling input; means for coupling the output of the first multivibrator to the trigger input of the second multivibrator to provide an input thereto to trigger the second multivibrator upon the termination of the output pulse from the first multivibrator; a gate, the output of the gate being connected to the trigger input of the first multivibrator to provide an input thereto; means for coupling the output of the second multivibrator to the gate to provide a first input thereto to trigger the first multivibrator upon the termination of the output pulse from the second multivibrator; an indicator device for receiving output pulses from the first multivibrator and for providing an output in response thereto; first and second input lines, the first input line connected to provide a second input to the gate and the second input line providing an input to the enabling input of the second multivibrator; means for coupling the second input line to the gate to provide a third input thereto; and means for selectively applying an input signal to the first or the second input lines, whereby an input signal on the first input line operating to trigger the first multivibrator to provide a single output from the indicator device, and an input signal on the second input line operating to both trigger the first multivibrator, and to enable the second multivibrator, so that the termination of the output from the first multivibrator operates to trigger the second multivibrator and so that the termination of the output from the second multivibrator operates to trigger the first multivibrator, the first and second multivibrators thereby being alternately triggered to provide a repetitive output from the indicator device in response to the repetitive triggering of the first multivibrator.
 8. A circuit as recited in claim 7, wherein at least one of the coupling means comprises a capacitor.
 9. A circuit as recited in claim 8, wherein each coupling means comprises a capacitor.
 10. A circuit as recited in claim 9, wherein the first multivibrator is constantly enabled to provide an output pulse in response to an input signal.
 11. A circuit as recited in claim 10, wherein: the indicator device is an audible alarm device; an amplifier is connected to provide an input to the alarm device in response to an input signal to the amplifier; and the output pulse of the first multivibrator provides an input signal to the amplifier. 